Dataset Information

Sorbent Film-Coated Passive Samplers for Explosives Vapour Detection Part B: Deployment in Semi-Operational Environments and Alternative Applications.

ABSTRACT: The application of new sorbent-film coated passive samplers for capture of bulk commercial and military explosives vapours in operationally relevant spaces such as luggage, rooms, vehicles and shipping containers is presented. Samplers were easily integrated with in-service detection technologies with little/no sample preparation required. Ethylene glycol dinitrate (EGDN) was detected within 4?h in a container holding a suitcase packed with 0.2?kg Perunit 28E. Within a 22,000?dm³ room, 1?kg of concealed Seguridad was detected within 24?h and in an adjoining room within 7 days. Exposed samplers also successfully captured components of 1?kg TNT after 72?h and 1?kg concealed Perunit 28E after 6?h in both a furnished room and a large, partially filled shipping container. For the latter, samplers captured detectable residues outside the container after 24?h and were stable during wet weather for 72?h. A one-week trial at three operationally relevant venues including a university, a theatre and a government building revealed a nuisance positive rate of <1.4% (n?=?72). Finally, two alternative applications are presented for extraction of liquid samples and use a particulate contact swab showing flexibility for a range of different search activities.

SUBMITTER: McEneff GL

PROVIDER: S-EPMC5895787 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Diffusive gradient in thin-film (DGT) passive samplers are frequently used to monitor the concentrations of metals such as mercury and zinc in sediments and other aquatic environments. The application of these samplers generally presumes that they quantify only the dissolved fraction and not particle-bound metal species that are too large to migrate into the sampler. However, metals associated with very small nanoparticles (smaller than the pore size of DGT samplers) can be abundant in certain environments, yet the implications of these nanoparticles for DGT measurements are unclear. The objective of this study was to determine how the performance of the DGT sampler is affected by the presence of nanoparticulate species of Hg and Zn. DGT samplers were exposed to solutions containing known amounts of dissolved Hg(II) and nanoparticulate HgS (or dissolved Zn(II) and nanoparticulate ZnS). The amounts of Hg and Zn accumulated onto the DGT samplers were quantified over hours to days, and the rates of diffusion of the dissolved metal (i.e., the effective diffusion coefficient D) into the sampler's diffusion layer were calculated and compared for solutions containing varying concentrations of nanoparticles. The results suggested that the nanoparticles deposited on the surface of the samplers might have acted as sorbents, slowing the migration of the dissolved species into the samplers. The consequence was that the DGT sampler data underestimated the dissolved metal concentration in the solution. In addition, X-ray absorption spectroscopy was employed to determine the speciation of the Hg accumulated on the sampler binding layer, and the results indicated that HgS nanoparticles did not appear to directly contribute to the DGT measurement. Overall, our findings suggest that the deployment of DGT samplers in settings where nanoparticles are relevant (e.g., sediments) may result in DGT data that incorrectly estimated the dissolved metal concentrations. Models for metal uptake into the sampler may need to be reconsidered.

Project description:Mercury is a risk in aquatic ecosystems when the metal is converted to methylmercury (MeHg) and subsequently bioaccumulates in aquatic food webs. This risk can be difficult to manage because of the complexity of biogeochemical processes for mercury and the need for accessible techniques to navigate this complexity. Here, we explored the use of diffusive gradient in thin-film (DGT) passive samplers as a tool to simultaneously quantify the methylation potential of inorganic Hg (IHg) and the bioaccumulation potential of MeHg in freshwater wetlands. Outdoor freshwater wetland mesocosms were amended with four isotopically labeled and geochemically relevant IHg forms that represent a range of methylation potentials (202Hg2+, 201Hg-humic acid, 199Hg-sorbed to FeS, and 200HgS nanoparticles). Six weeks after the spikes, we deployed DGT samplers in the mesocosm water and sediments, evaluated DGT-uptake rates of total Hg, MeHg, and IHg (calculated by difference) for the Hg isotope spikes, and examined correlations with total Hg, MeHg, and IHg concentrations in sediment, water, and micro and macrofauna in the ecosystem. In the sediments, we observed greater relative MeHg concentrations from the initially dissolved IHg isotope spikes and lower MeHg levels from the initially particulate IHg spikes. These trends were consistent with uptake flux of IHg into DGTs deployed in surface sediments. Moreover, we observed correlations between total Hg-DGT uptake flux and MeHg levels in periphyton biofilms, submergent plant stems, snails, and mosquitofish in the ecosystem. These correlations were better for DGTs deployed in the water column compared to DGTs in the sediments, suggesting the importance of vertical distribution of bioavailable MeHg in relation to food sources for macrofauna. Overall, these results demonstrate that DGT passive samplers are a relatively simple and efficient tool for predicting IHg methylation and MeHg bioaccumulation potentials without the need to explicitly delineate IHg and MeHg speciation and partitioning in complex ecosystems.

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Dataset Information

Sorbent Film-Coated Passive Samplers for Explosives Vapour Detection Part B: Deployment in Semi-Operational Environments and Alternative Applications.

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